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A229421 Number of n X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, rows lexicographically nondecreasing, and columns lexicographically nonincreasing.

%I A229421 #14 Feb 09 2019 11:08:14
%S A229421 3,12,83,754,7816,87648,1037193,12768612,162034856,2106287556,
%T A229421 27919532994,376116911288,5136301331502,70961712401226,
%U A229421 990271481453131,13940677426765198,197768065242681646,2824828320413979786,40595088421065998006,586585037559246948950
%N A229421 Number of n X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, rows lexicographically nondecreasing, and columns lexicographically nonincreasing.
%H A229421 Alois P. Heinz, <a href="/A229421/b229421.txt">Table of n, a(n) for n = 1..40</a>
%e A229421 Some solutions for n=4
%e A229421 ..1..1..0..0....1..1..1..1....0..0..0..0....2..2..1..1....2..1..1..0
%e A229421 ..1..1..0..0....2..1..1..1....1..1..0..0....2..2..2..1....2..1..1..0
%e A229421 ..2..1..1..0....2..2..1..1....2..1..1..1....2..2..2..1....2..1..1..1
%e A229421 ..2..1..1..0....2..2..2..1....2..2..2..1....2..2..2..2....2..2..2..2
%Y A229421 Diagonal of A229428.
%K A229421 nonn
%O A229421 1,1
%A A229421 _R. H. Hardin_, Sep 22 2013
%E A229421 a(16)-a(20) from _Alois P. Heinz_, Feb 08 2019